Mechanoluminescence of Bi‐Activated NaYGeO₄ Polycrystals and 3D Printed Scaffolds in the NUV/Blue and NIR Spectral Range

Abstract Mechanoluminescent (ML) materials emit light when mechanically stimulated, serving as sensors and light sources in applications such as stress sensing, anti‐counterfeiting, and biomechanical imaging. ML in the ultraviolet and near‐infrared regions can trigger light‐induced processes in living organisms, offering potential for photodynamic therapy and diagnostics. However, bismuth‐doped materials with UV and NIR ML are rarely reported. Herein, a series of NUV/Blue and NIR ML phosphors, NaY_1‐xBi_xGeO₄ (NYGOB_x) (0.0 ≤ x ≤ 4.0 mol%), with mechanically induced (impact and scratching) and NIR persistent photoluminescence (pPL) characteristics are developed using a conventional solid‐state reaction method. XPS and photoluminescence (PL) characterizations indicate the coexistence of bismuth in multiple valence states. The optimal NYGOBi_1.5 sample exhibits broadband UV/blue emission (325–525 nm, centered at 405 nm, PLQY of 45.70%, and FWHM of 63.70 nm), along with broadband NIR emission (900–1600 nm). The combination of NUV/blue (∼415 nm), NIR‐I (∼825 nm), and NIR‐II (∼1235 nm) pPL from Bi³⁺, Bi²⁺, and Bi⁺, respectively, is observed, with the durations of up to ∼100 s. A scratch‐induced ML is visualized on a 3D‐printed ML scaffold prepared using stereolithography (SLA) 3D printing technology, suggesting its potential application for functional lighting devices.